表达式6: StartFraction, left parenthesis, left parenthesis, tan to the negative 1st power left parenthesis, StartNestedFraction, StartNestedFraction, "L" NestedOver 2 , EndNestedFraction NestedOver "f" , EndNestedFraction , right parenthesis , right parenthesis times 2 , right parenthesis Over pi , EndFraction times 180tan−1L2f·2π·180